1. Field of the Invention
The present invention relates generally to the fabrication of semiconductor devices and to chemical mechanical polishing and planarization of semiconductor devices.
2. Background of the Related Art
In the fabrication of integrated circuits and other electronic devices, multiple layers of conducting, semiconducting, and dielectric materials are deposited on or removed from a surface of a substrate. Thin layers of conducting, semiconducting, and dielectric materials may be deposited by a number of deposition techniques. Common deposition techniques in modern processing include physical vapor deposition (PVD), also known as sputtering, chemical vapor deposition (CVD), plasma-enhanced chemical vapor deposition (PECVD), and now electrochemical plating (ECP).
As layers of materials are sequentially deposited and removed, the uppermost surface of the substrate may become non-planar across its surface and require planarization. Planarizing a surface, or xe2x80x9cpolishingxe2x80x9d a surface, is a process where material is removed from the surface of the substrate to form a generally even, planar surface. Planarization is useful in removing undesired surface topography and surface defects, such as rough surfaces, agglomerated materials, crystal lattice damage, scratches, and contaminated layers or materials. Planarization is also useful in forming features on a substrate by removing excess deposited material used to fill the features and to provide an even surface for subsequent levels of metallization and processing.
Chemical mechanical planarization, or chemical mechanical polishing (CMP), is common technique used to planarize substrates. CMP utilizes a chemical composition, typically a slurry or other fluid medium, for selective removal of material from substrates. In conventional CMP techniques, a substrate carrier or polishing head is mounted on a carrier assembly and positioned in contact with a polishing pad in a CMP apparatus. The carrier assembly provides a controllable pressure to the substrate urging the substrate against the polishing pad. The pad is moved relative to the substrate by an external driving force. Thus, the CMP apparatus effects polishing or rubbing movement between the surface of the substrate and the polishing pad while dispersing a polishing composition, or slurry, to effect both chemical activity and mechanical activity.
Conventional CMP processes are performed using an abrasive article, such as a polishing composition, or slurry, containing abrasive particles in a reactive solution with a conventional polishing pad. Alternatively, the abrasive article can be a fixed abrasive article, such as a fixed abrasive polishing pad, which may be used with a CMP composition or slurry that does not contain abrasive particles. A fixed abrasive article typically comprises a backing sheet with a plurality of geometric abrasive composite elements adhered thereto.
Conventional CMP techniques employing polishing pads utilizing CMP compositions containing abrasive particles as well as CMP techniques employing fixed abrasive articles are subject to dishing as a result of overpolishing. Dishing occurs when a portions of the surface of a metal deposited in an aperture or other substrate structure formed in a dielectric layer is excessively polished resulting in one or more concavities or depressions. Dishing performance is used to describe the ability of a CMP composition or process to polish and planarize a surface without dishing or with reduced dishing of the surface. Corrosion inhibitors are added to CMP compositions to reduce dishing, improve dishing performance, and prevent corrosion of materials during the CMP process. The corrosion inhibitors prevent or reduce the corrosion of the metal surfaces.
However, CMP compositions containing corrosion inhibitors have been observed to have reduced metal dissolution during polishing and decreased solubility of polishing by-products, such as metal ions, in comparison to CMP compositions without corrosion inhibitors. The reduced metal dissolution and decreased by-product solubility in CMP compositions can result in deposition or re-deposition of metals and by-products on the substrate during the CMP process. Metals and by-products deposited during CMP processes have been observed to remain as undesirable metal residues after the CMP process and detrimentally affect the polish quality of the substrate surface.
Therefore, there exists a need for a method and CMP composition that reduces the deposition or re-deposition of materials during CMP processing.
The invention generally provides a method and composition for planarizing a substrate surface with reduced re-deposition of metal during the CMP process. In one aspect, the invention provides a composition for planarizing a substrate, the composition comprising one or more surfactants including one or more anionic surfactants, Zweitter-ionic surfactants, dispersers, or combinations thereof, one or more chelating agents, one or more oxidizers, one or more corrosion inhibitors, and deionized water. The composition may further include one or more agents to adjust the pH of the composition. The CMP composition may also include an abrasive particle concentration of about 35 wt. % or less.
In another aspect, the invention provides a method for removing at least a portion of a material from a substrate surface, the method comprising planarizing the substrate surface using a composition including one or more anionic surfactants, Zweitter-ionic surfactants, dispersers, or combinations thereof. The composition further comprises one or more chelating agents, one or more oxidizers, one or more corrosion inhibitors, deionized water, and may optionally include one or more agents to adjust the pH of the composition or abrasive particles.
Another aspect of the invention provides a method for processing a substrate, comprising forming an aperture in the surface of a substrate, depositing a barrier layer on the surface of the substrate, depositing a metal layer on the barrier layer to fill the aperture, and planarizing the substrate to remove the metal layer above the surface of the substrate using a composition comprising one or more anionic surfactants, Zweitter-ionic surfactants, dispersers, or combinations thereof, one or more chelating agents, one or more oxidizers, one or more corrosion inhibitors, and deionized water. The composition may further comprise one or more agents to adjust the pH of the composition or abrasive particles.